In recent years, the number of store-based walk-in medical clinics has mushroomed. The clinics, typically staffed by nurse practitioners who treat routine medical problems, have been hailed by many in the healthcare field as a way to improve access to care and cut costs. Although located in big-name stores like CVS, Walgreens, and Wal-Mart, however, many of the clinics are bankrolled by third parties, and they�ve been pulling the plug on some that haven�t been profitable. The number of retail clinics nationwide dropped for the first time last month, falling from 981 to 969, leading some industry observers to speculate that the boom may be over. Last year, retail clinics were opening at a rate of one a day.